The present invention relates to a heat shrinkable shielding tube for shielding electrical wires from external electromagnetic radiation and preventing such radiation generated by the wires from emanating outside of the shielding tube.
This invention pertains to an electromagnetic shielding tube which can be easily fitted around an electric wire or bundle of wires and fixed thereto by a heating process.
A heat shrinkable tube is a rubber or plastic tube which shrinks in all dimensions when exposed to heat. Such tubes are used to protect or fix electric wires or cables inserted within the tube. The tube generally has a seamless tubular shape. The tubes are made of material such as polyolefin, Teflon or polyvinyl chloride (PVC). When an electric wire or cable is inserted into the shielding tube and heat is applied, the tube constricts, causing the inner surface of the tube to tightly engage the outside surface of the electric wires within in order to protect and fix them.
However, such heat shrinkable tubes do not effectively prevent the electromagnetic radiation generated by a current flowing in the contained electric wires from emanating from the tube nor do they prevent electromagnetic radiation generated externally from penetrating the heat shrinkable tube which can affect the electrical performance of the contained wires. Such electromagnetic interference can create problems in electronic appliances or telecommunication products sensitive to electromagnetic radiation, possibly causing the products to operate erroneously or reduce their sensitivity.
Previously, a common approach was to spirally wrap a tape made from an electromagnetic shielding material around the outside surface of the electric wires to be shielded. The electric wire wound by the shielding material was then inserted into the heat shrinkable tube. When heat was applied, the heat shrinkable tube constricted around the tape shielded wires, thereby fixing the wires and their shielding.
There are still several problems with this approach. Wrapping the wires with an electromagnetically shielding tape is a relatively time consuming and complex operation. Also, such a configuration requires a certain amount of overlapping of the electromagnetic shielding material, which raises the material costs for the shielding. In addition, it is difficult to obtain a uniform shielding affect from this method of shielding.